Smoking has been determined to be a contributory or causative factor in a number of diseases including respiratory diseases such as emphysema, chronic bronchitis, lung infections and lung cancer. Most regular smokers become addicted to, or dependent upon, the pharmacological effects of nicotine in tobacco smoke. A common strategy in overcoming a nicotine addiction is the administration of daily doses of nicotine which are therefrom gradually reduced until complete elimination.
It is believed that cigarette smoke contains approximately 4000 chemical compounds and has a range of particle sizes from less than 0.1 micron to approximately 0.5 micron. During inhalation, it is known that most particles larger than 10-12 micron in size typically can't make the turn in the oral cavity to enter the lower respiratory tract and instead impact the back of the throat. While particles less than 5 micron in size are generally considered respirable and can thus enter the lower respiratory tract, the majority of particles less than 1 micron in size do not settle in the alveoli, and are thus expelled during subsequent exhalation.
The state of the art in the development of nicotine inhalation products designed to replace traditional cigarettes, is to replicate or match the particles found in cigarettes. For example, such replacement technologies include e-cigarettes that produce nicotine vapor, ultrasonically produced nicotine aerosol droplets or nicotine oral sprays. These replacement cigarette technologies typically produce particles that are less than 0.5 micron in size, and very large particles that are greater than 10-12 micron in size. However, each of these technologies suffer from the same result—in that less than half of the inhaled nicotine and associated compounds remain in the lungs and the balance is exhaled into the environment. Unfortunately, this means that the public must still contend with the same problem of users of these technologies producing what is effectively second hand smoke, and accordingly these technologies are increasingly being banned in selected public spaces.
Self-propelled aerosols (also known as pressurized aerosols) which contain nicotine in solution have also been proposed as cigarette substitutes. An example is the self-propelled formulation of Jacobs (U.S. Pat. No. 4,635,651). As shown in Jacobs, these delivery systems contain a water-based aerosol formulation and a propellant such as freon, which are stored in a pressurized container. When actuated, Jacobs delivers nicotine and a solid carrier to the mouth of the user. Thus the aerosol created by Jacobs contains, in combination, a mixture of nicotine and the solid carrier. The nicotine is not formed as a composite part of the solid carrier. Further, the particle size of the aerosol created by Jacobs was variable. Therefore, the dose which is administered by using such pressurized aerosols may not be accurately controlled. It has also been proposed to produce a dry powder inhaler for delivering a nicotine containing medicament via inhalation (see PCT application PCT/CA95/00562).
While nicotine formulations in the form of salts and complexes have been developed, there is still a need for nicotine formulations adapted for inhalation into the alveoli and smaller airways of the lungs, while reducing or eliminating exhalable nicotine by a subject. The present invention satisfies this need.